JPH09279092A - Coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a coating film excellent in curing characteristics, finished properties, and yellowing resistance by using zinc octanoate as an urethane curing catalyst and aniline oxalate as an ultraviolet absorbing agent. SOLUTION: In this method, use is made of a hydroxyl group-containing copolymer (A), a polyisocyanate compound (B), a urethane curing agent (C), and an ultraviolet curing advent (D). As the component (A), a hydroxyl group- containing copolymer with two or more hydroxyl groups in the molecule particularly preferably having a hydroxyl value of 40 to 200 and a weight-average molecular weight of 4,000 to 30,000 obtained by copolymerizing a hydroxyl group-containing monomer (e.g. hydroxyethyl acrylate) with other monomer (e.g. methyl methacrylate) is preferable. As the component (B), for example, hexamethylene diisocyanate is used with the B/A (equivalent ratio) being 0.5 to 2.0. As the component (C), zinc octanoate is used and as the component (D), aniline oxalate is used, each which is used in an amount of 0.1 to 5wt.% based on the solid resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition capable of forming a coating film excellent in curability, finish and yellowing resistance.

[0002]

2. Description of the Related Art Conventionally, acrylic lacquer, acrylic urethane paint, etc. have been used for automobile repair and coating / repair of industrial machines, buildings, etc. Acrylic urethane paints are the mainstream as repair paints. As a urethane curing catalyst for such paint, metal ions, third
Examples thereof include primary amines and organometallic compounds. Of these, organotin compounds are commonly used in topcoat paints because they do not discolor and impart curability with a small amount of addition. .

However, when the addition amount of the organotin compound is increased for the purpose of further improving the curability, the finish property tends to be deteriorated such as the occurrence of gloss. Therefore, it has also been proposed to use a tertiary amine in combination with the organotin compound, whereby both curability and finish can be achieved, but there has been a problem that the coating liquid or coating film turns yellow. In particular, when the ultraviolet absorber was present in the same coating film or in the adjacent coating films, it turned yellow severely and could not be used as a top coat.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that by combining a urethane curing catalyst and an ultraviolet absorber in a specific combination, curability, finish and yellowing resistance are improved. The inventors have found that a coating composition capable of forming an excellent coating film can be obtained, and arrived at the present invention.

That is, the present invention is a coating composition containing a hydroxyl group-containing copolymer, a polyisocyanate compound, a urethane curing catalyst and an ultraviolet absorber, wherein the urethane curing catalyst is zinc octylate and The present invention provides a coating composition characterized in that the absorbent is anilide oxalic acid.

Hereinafter, the present invention will be described in detail.

In the present invention, the hydroxyl group-containing copolymer is 1
A polymer having two or more hydroxyl groups in the molecule, and particularly, a hydroxyl value of 40 to 200 and a weight average molecular weight of 4000 to 3 formed by copolymerizing a hydroxyl group-containing monomer with another monomer.
50,000 hydroxyl group-containing copolymers are preferred.

Examples of the hydroxyl group-containing monomer include hydroxyalkyl esters of (meth) acrylic acid such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate; hydroxyalkyl esters of (meth) acrylic acid. Addition products with lactones; monoesters of polyethylene glycol, polypropylene glycol, and other polyether polyols with (meth) acrylic acid, and other unsaturated carboxylic acids; polypropylene glycol, and other polyether polyols And a hydroxyl group-containing monomer such as hydroxyethyl (meth) acrylate, an adduct of an unsaturated carboxylic acid such as (meth) acrylic acid and a monoepoxy compound, and the like.

Other monomers include, for example, methyl (meth) acrylate, ethyl (meth) acrylate,
Propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl ( (Meth) acryl
, Lauryl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate,
Alkyl ester of (meth) acrylic acid such as isobornyl (meth) acrylate; C2-18 alkoxyalkyl ester of acrylic acid or methacrylic acid such as methoxyethyl (meth) acrylate and ethoxybutyl (meth) acrylate. Vinyl aromatic compounds such as styrene, α-methylstyrene, vinyltoluene, α-chlorostyrene; perfluorobutylethyl (meth) acrylate, perfluoroisononylethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate, etc. A perfluoroalkyl (meth) acrylate of
CF2 = CF2, CHF = CF2, CH2 = CF2, C
General formula CX2 = CX2 such as ClF = CF2 (wherein X is the same or different and represents H, Cl, Br, F, an alkyl group or a haloalkyl group, provided that at least one F is contained in the formula. And a polymer of one or more of these monomers, which has a copolymerizable double bond at one end, a so-called macromonomer and a hydroxyl group-containing monomer. Examples of other copolymerizable monomers. These can be appropriately selected and used according to desired physical properties.

Examples of the solvent used in the solution polymerization of the above monomer mixture include alkylbenzene derivatives such as benzene, toluene and xylene; ethyl acetate, propyl acetate, amyl acetate, methoxybutyl acetate, methyl acetoacetate, ethyl acetoacetate and acetic acid. Acetate ester solvents such as methyl cellosolve, cellosolve acetate, diethylene glycol monomethyl ether acetate and carbitol acetate;
Ether solvents such as dioxane, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol diethyl ether; acetone,
Examples of the solvent include ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, which may be used alone or in combination of two or more.

As the radical polymerization initiator, benzoyl peroxide, di-t-butyl hydroperoxide, t-butyl hydroperoxide, cumyl peroxide,
Peroxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, t-butylperoxybenzoate, lauryl peroxide, acetyl peroxide, t-butylperoxy-2-ethylhexanoate; α, α′-azo Examples thereof include azo compounds such as bisisobutyronitrile, α, α′-azobis-2-methylbutyronitrile, azobisdimethylvaleronitrile and azobiscyclohexanecarbonitrile.

The above hydroxyl group-containing copolymer has a hydroxyl value of 40.
It is desirable to be in the range of -200, preferably 60-160. If it deviates from this range, the crosslinking point becomes insufficient and the curability becomes insufficient. On the other hand, if the hydroxyl group becomes excessive, the water resistance and the drying property of the coating film are adversely affected, which is not preferable.

The above hydroxyl group-containing copolymer has a weight average molecular weight of 4,000 to 30,000, preferably 5,000.
It is desirable to be in the range of 20,000. If it deviates from this range, the workability of coating and finish of the coated surface are adversely affected, which is not preferable.

Further, it is desirable that the hydroxyl group-containing copolymer has a glass transition temperature of 40 to 110 ° C., preferably 50 to 90 ° C. If it deviates from this range, the workability in painting, the workability in polishing, the weather resistance, etc. are adversely affected, which is not preferable.

In the present invention, as the polyisocyanate compound, conventionally known compounds can be used, for example, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, isophorone diisocyanate. -, Hydrogenated diphenylmethane diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, lysine diisocyanate; excess of these diisocyanates in water, ethylene glycol
-Terminal compounds containing isocyanate, which are obtained by reacting low-molecular active hydrogen-containing compounds such as propylene, propylene glycol and trimethylolpropane, and these polyisocyanates
Examples thereof include polymers of compound and burette.

The ratio of the hydroxyl group-containing copolymer to the polyisocyanate compound used is [isocyanate group in the polyisocyanate compound] / [hydroxyl group in the hydroxyl group-containing copolymer] = 0.5 to 2 It is suitable to select the equivalence ratio within the range of 0.0.

In the present invention, zinc octylate is used as a urethane curing catalyst. Further, an organic tin compound may be used together if necessary. The content of the zinc octylate is appropriately 0.1 to 5% by weight, preferably 0.2 to 2% by weight, based on the resin solid content. If the content is less than 0.1% by weight, good curability cannot be obtained, while if it exceeds 5% by weight, the finished appearance is deteriorated, which is not preferable.

Further, in the present invention, oxalic acid anilide is used as an ultraviolet absorber. The content of the oxalic acid anilide is 0.1 to 5% by weight, preferably 0.3 to 3% by weight, based on the resin solid content. If the content is less than 0.1% by weight, the weather resistance is adversely affected, while if it exceeds 5% by weight, the coating liquid tends to be colored, which is not preferable.

The composition of the present invention contains the above-mentioned hydroxyl group-containing copolymer, polyisocyanate compound, zinc octylate and anilide oxalic acid as essential components, and if necessary, pigments and fibrin derivatives. , An additive resin, a light stabilizer, a surface conditioner, and other paint additives.

The composition of the present invention thus obtained is generally used just before coating by mixing a main agent containing a hydroxyl group-containing copolymer, zinc octylate and anilide oxalic acid with a curing agent containing a polyisocyanate compound. It

As a method for coating the composition of the present invention, conventionally known methods such as spray coating, brush coating and roller coating can be used. Usually, a dry film thickness of about 10 to 100 μm is applied.

[0022]

The present invention will be described below in detail with reference to examples. In the text, "part" and "%" mean "part by weight" and "% by weight", respectively.

Production of hydroxyl group-containing copolymer A reactor is equipped with a thermometer, a thermostat, a stirrer, a reflux condenser and a dropping pump, and 33 parts of toluene and 10 parts of xylene are charged therein, and the temperature is raised to 110 ° C. with stirring. 20 parts of styrene, 30 parts of methyl methacrylate, t
-Butyl methacrylate 16 parts, i-butyl acrylate
3 parts, hydroxyethyl acrylate 17 parts, 2-ethylhexyl acrylate 13 parts, acrylic acid 1 part and t-butyl peroxyoctanoate 6 parts, a mixture of a monomer and a polymerization initiator 106. A part was added dropwise at a constant rate at 110 ° C. or lower for 3 hours using a dropping pump. After completion of dropping, the temperature was kept at 110 ° C. for 60 minutes, and stirring was continued. Thereafter, a solution prepared by dissolving 0.5 parts of additional catalyst azobisdimethylvaleronitrile in 10 parts of xylene was added dropwise at a constant rate over 60 minutes. And 110 minutes at the end of the drip for 60 minutes
And the reaction was completed. The resulting hydroxyl group-containing copolymer solution was a uniform transparent solution having a nonvolatile content of 65%.
The weight average molecular weight of the copolymer was 10,000, the hydroxyl value was 82, and the glass transition temperature was 32 ° C.

Examples and Comparative Examples Using the hydroxyl group-containing copolymer solution obtained in the above Production Example, a curing catalyst and an ultraviolet absorber were further compounded as shown in Table 1 to prepare a base material for clear paint. Next, as shown in Table 1, a polyisocyanate compound which is a curing agent was added to the base material for clear coating composition, and the mixture was mixed and stirred to obtain each clear coating composition.

Each clear coating was applied to xylene / butyl acetate /
Shell Zol A (Aromatic petroleum solvent manufactured by Shell Chemical Co., Ltd.) =
With a thinner having a composition of 60/20/20, the viscosity was adjusted to 15 seconds at a fore cup # 4/25 ° C., and a dry film thickness of 40 μm was applied on a process plate coated with a clear paint for a new car at 20 ° C. After the spray coating was performed so that the above, the coating film performance was evaluated. Table 2 shows the results.

[0026]

[Table 1]

[0027]

[Table 2]

The tests in Table 2 were conducted according to the following method.

(1) Dryability After coating at 20 ° C., the coated plate was kept horizontally for 20 minutes, and then 60
It was left to stand for 60 minutes in a dryer whose temperature was set to ° C. After taking out the test plate from the dryer, the temperature is 20 ° C and the humidity is 75% R.
It is left standing in a room of constant temperature and humidity of H, and after standing for 2 hours, 8 pieces of gauze are placed on the surface of the coating film, and the contact area 1 is placed on it.
A 200 g weight of 2.56 cm ² was placed for 1 minute, and the trace of the gauze immediately after that was visually evaluated according to the following criteria.

○: No trace of gauze △: Slight trace of gaze ×: Mark of trace of gauze (2) Pencil hardness 7 The coated plate was placed in a constant temperature and humidity chamber at a temperature of 20 ° C. and a humidity of 75% RH.
After standing for a day, the coated plate was subjected to a pencil scratching test at the same temperature to examine the hardness of the pencil with which the coating film had a flaw. (3) Adhesiveness A coated sheet made in the same manner as in (2) above should have 1 square stitch
00 pieces were drawn, and the number of eyes remaining when peeled off with cellophane tape was displayed.

(4) Water resistance The coated plate prepared in the same manner as in (2) above was immersed in tap water at 20 ° C. for 7 days, and then the state of the coated surface was examined.

◯: No abnormality X: Blistering occurred (5) Gasoline resistance A coated plate prepared in the same manner as in (2) above was fixed horizontally,
Approximately 5 cc of regular type gasoline was soaked in a gauze (50 × 50 mm) folded in four, and left as it was for 3 minutes. After that, the gauze was removed, and the state of the coated surface was examined after the gasoline was wiped off with another gauze.

◯: No abnormality X: Decrease in gloss and softening of coated surface occur (6) Acid resistance / alkali resistance On a coated plate prepared in the same manner as in the above (2), 0.2 N sulfuric acid aqueous solution, 0. Spot 2N NaOH aqueous solution and leave it at 20 ° C for 24 hours for whitening and blistering.
The presence or absence was visually determined.

◯: No abnormality X: Whitening or blister generation (7) Erichsen value A coated plate coated on a steel plate is left in a constant temperature and humidity chamber at 20 ° C and 75% RH for 7 days, and then the test piece is subjected to Erichsen test at 20 ° C. The punch with a radius of curvature of 10 mm was attached to the machine and extruded from the back surface of the test piece at a specified distance at a speed of about 0.1 mm / sec to find the extrusion distance (mm) when the coating film was cracked or peeled. The Erichsen value was used.

(8) Impact resistance According to JIS K-5400, a test was conducted using a DuPont impact tester under the conditions that the tip diameter of the impact core was 1/2 inch and the load was 500 g. Maximum height (cm) that does not cause coating film damage
Is shown.

(9) Accelerated weathering resistance The coated plate prepared in the same manner as in the above (2) was tested by a sunshine weatherometer for 1000 hours, and the coated surface state and yellowing were visually judged.

(Coating state) ∘: Almost no change on coating surface ×: Water marks are observed on coating surface, resulting in a large decrease in gloss (yellowing) ○: No yellowing ×: Yellowing (10) Finished Appearance The smoothness and transparency of the coating film of the coated plate prepared in the same manner as in (2) above were visually determined, and the gloss (20 ° gloss) was measured.

◯: Good Δ: Slightly bad ×: Poor (11) Yellowing of coating liquid The main agent used in the clear coating composition was stored at 40 ° C. for 1 month in a thermostatic chamber. APHA was used as the base liquid at the beginning of storage and after storage.
A standard solution with a chromaticity of 0-500 (the higher the number, the more colored it is) determined by the concentration of the cobalt chloride / potassium chloroplatinate solution according to the (American Public Health Assn.) Method and visually And the chromaticity of the standard solution corresponding to the color of the main agent solution after the initial storage and after the storage (AP
HA value) was investigated. The difference between the APHA value of the main agent liquid after storage and the APHA value of the main agent solution at the initial storage was evaluated by ΔAPHA.

○: ΔAPHA is 0 to less than 20 Δ: 〃 20 to less than 40 ×: 〃 40 or more

[0040]

EFFECTS OF THE INVENTION According to the present invention, a coating composition capable of forming a coating film excellent in curability, finish and yellowing resistance is obtained by using a specific combination of a urethane curing catalyst and an ultraviolet absorber. can get. The composition of the present invention is useful in the field of automobile repair paints.

Claims (1)

[Claims] 1. A hydroxyl group-containing copolymer, polyisocyanate
A coating composition containing a compound, a urethane curing catalyst and an ultraviolet absorber, the coating composition comprising zinc octylate as the urethane curing catalyst and oxalic acid anilide as the ultraviolet absorber. Composition.